That port measurement looks very clean!
There is something happening around 120Hz, that also shows on my measurement (could be a coincidence though).

Regarding tuning measurement, here are two methods:
A simple and precise one described by sebackman here: http://www.audioheritage.org/vbullet...l=1#post388697
A less precise but even simpler one that I described here: http://www.audioheritage.org/vbullet...l=1#post388714